Cell module

ABSTRACT

A cell module includes a plurality of battery cells each having a safety valve at a first end in a height direction, a first current collector plate including a main body having a through hole that at least partly overlaps the safety valve when viewed along the height direction and a lead extending into the through hole from the main body and being electrically connected to a first terminal of each of the battery cells, an exhaust duct disposed over a surface of the first current collector plate remote from the battery cells, and an insulating film being made of an insulating material and covering an area of the first current collector plate facing the exhaust duct. The safety valve opens when an internal pressure of any of the battery cells reaches or exceeds a predetermined level.

This application is a U.S. national stage application of the PCTInternational Application No. PCT/JP2017/040172 filed on Nov. 8, 2017,which claims the benefit of foreign priority of Japanese patentapplication No. 2016-231959 filed on Nov. 30, 2016, the contents all ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a cell module.

BACKGROUND ART

A conventional cell module, as described in PTL 1, includes a pluralityof battery cells arranged in a matrix. Positive electrode terminals ofthe battery cells are electrically connected to a positive-electrodecurrent collector plate made of a conductive flat board, whereasnegative electrode terminals of the battery cells are electricallyconnected via fuses to a negative-electrode current collector plate madeof a conductive flat board. Thus, the cell module has the plurality ofthe parallel-connected battery cells and is designed to separate anybattery cell through which a large current greater than or equal to arated current has flowed from an electric circuit by blowing the fuse ofthe battery cell with Joule heat. This configuration prevents thebattery cell from abnormally generating heat due to the flow of largecurrent through the battery cell.

As described in PTL 2, a cell module has a safety valve on one end faceof each battery cell in a height direction. The cell module isconfigured to let the safety valve break and discharge an emissionincluding a high-temperature gas from any of the battery cells if thebattery cell reaches an abnormally high temperature and the pressureinside the battery cell rises. The discharged emission passes through athrough hole formed in a place of a current collector plate overlappingthe battery cell in the height direction and is guided into an exhaustduct disposed over a surface of the current collector plate remote fromthe battery cells. This configuration allows the emission to flowthrough the exhaust duct and be discharged outside from an outlet of theexhaust duct and thereby hinders the emission including thehigh-temperature gas discharged from the abnormally high-temperaturebattery cell from having an impact on the other battery cells.

CITATION LIST Patent Literature

PTL 1: International Patent Publication No. 2012/073403

PTL 2: Unexamined Japanese Patent Publication No. 2013-47873

SUMMARY OF THE INVENTION Technical Problem

The emission discharged from the battery cell due to a brake in thesafety valve described above contains many conductive materials such ascopper foil. If these conductive materials extend between a positiveelectrode of the battery cell and the current collector plate, a path ofthe conductive materials is formed between the positive electrode of thebattery cell and the current collector plate and an electric currentflows into the path of the conductive materials. Thus, an electriccircuit originally designed in the module is changed into a verydifferent one. In addition, the path of the conductive materials hindersa large current from flowing into a fuse for the abnormallyhigh-temperature battery cell. As a result, the fuse may not be blown.This prevents the separation of the abnormally high-temperature batterycell from the circuit of the parallel-connected battery cells, so thatthe abnormally high-temperature battery cell may further generate heatbecause of an electric current flowing inside.

It is an object of the present disclosure to provide a cell module thathinders a conductive material contained in an emission from a batterycell from forming a path between an electrode of the battery cell and acurrent collector plate and thus enables reliable separation of thebattery cell having reached an abnormally high temperature from anelectric circuit.

Advantageous Effect of Invention

A cell module according to the present disclosure includes a pluralityof battery cells that each includes a battery element and a cell casecontaining the battery element and having a safety valve at a first endin a height direction, the safety valve being configured to open when aninternal pressure inside the cell case reaches or exceeds apredetermined level, and a first current collector plate configured toelectrically connect first terminals of the plurality of the batterycells. The first current collector plate includes a main body having athrough hole that at least partly overlaps the safety valve when viewedalong the height direction, and a lead extending into the through holefrom the main body and being electrically connected to the firstterminal of each of the battery cells. The cell module further includesan exhaust duct disposed over a surface of the first current collectorplate remote from the battery cells, the exhaust duct being configuredto guide an emission being discharged from at least one of the pluralityof the battery cells and passing through the through hole to an outsideof the cell module when the safety valve of the at least one batterycell is opened, and an insulating film being made of an insulatingmaterial and covering an area of the first current collector platefacing the exhaust duct.

Advantageous Effect of Invention

In the cell module according to the present disclosure, the area of thefirst current collector plate facing the exhaust duct is covered withthe insulating film. Hence, even if an emission containing a conductivematerial flows into the exhaust duct such that a path of the conductivematerial is formed to join an inner surface of the exhaust duct and anelectrode of any of the battery cells together, the insulating filmprevents the path from reaching the first current collector plate.Accordingly, the emission discharged into the exhaust duct does notestablish any electrical connection between the electrode of the batterycell and the first current collector plate. This configuration hinders aconductive material contained in an emission from a battery cell havingreached an abnormally high temperature from forming a path to a currentcollector plate and thus enables reliable separation of the abnormallyhigh-temperature battery cell from an electric circuit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of a cell module according toa first exemplary embodiment of the present disclosure, viewed alongcentral axes of two or more cylindrical cells out of a plurality ofcylindrical cells included in the cell module.

FIG. 2 is a top plan view of a part of the cell module overlapping oneof the cylindrical cells, omitting illustration of a case.

FIG. 3 is a plan view of the part of the cell module in FIG. 2, omittingillustration of an insulating film.

FIG. 4 is a schematic cross-sectional view illustrating a problem with astructure of a cell module in a reference example, viewed along acentral axis of a cylindrical cell with a safety valve opened due toabnormal heat generation.

FIG. 5 is a schematic cross-sectional view of a structure correspondingto the structure of FIG. 4 in the cell module according to the firstexemplary embodiment.

FIG. 6 is a schematic cross-sectional view of a cell module according toa second exemplary embodiment of the present disclosure, viewed in thesame way as FIG. 1.

FIG. 7 is a schematic cross-sectional view of a structure correspondingto the structure of FIG. 5 in the cell module according to the secondexemplary embodiment.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments of the present disclosure will now be described indetail with reference to the attached drawings. It is initiallyenvisaged that a new exemplary embodiment can be made by suitablycombining some distinctive elements in any of the exemplary embodimentsand modifications described hereafter. In the description givenhereinafter, cylindrical cells 11 are incorporated in cell module 10 anda side of each cylindrical cell 11 adjacent to a positive electrode(adjacent to exhaust duct 70) in a height direction (in an axisdirection) is defined as an upper side.

First Exemplary Embodiment

FIG. 1 is a schematic cross-sectional view of cell module 10 accordingto a first exemplary embodiment of the present disclosure, viewed alongcentral axes of two or more cylindrical cells 11 out of a plurality ofcylindrical cells 11 included in cell module 10.

As shown in FIG. 1, cell module 10 includes a plurality of cylindricalcells 11 and cell holder 20 having a plurality of containers 18 tocontain cylindrical cells 11. In the example shown in FIG. 1, theplurality of containers 18 is arranged in a matrix when viewed fromabove, with a left-right direction of the figure representing onedirection and a direction perpendicular to the figure representing theother direction. However, the plurality of the containers may bearranged in a staggered manner when viewed from above.

Cylindrical cell 11 is an example of a battery cell and is, for example,formed of a secondary cell such as a lithium ion secondary cell.Cylindrical cell 11 includes cell case 12 made of metal, a batteryelement (not shown) contained in cell case 12, a positive electrodeterminal, and a negative electrode terminal. The battery elementincludes a pair of electrodes and a non-aqueous electrolyte to permitthe transfer of electric charge. Cell case 12 is made up of cell casebody 13 that is formed in a bottomed cylindrical shape to contain thebattery element and sealing plate 14 sealing an opening of cell casebody 13. Sealing plate 14 has safety valve 16. Safety valve 16 includesannular breaking portion 15 that breaks first when an internal pressureof the cell exceeds a predetermined level and a portion surrounded bybreaking portion 15. The sealing plate is electrically connected to apositive electrode of the battery element. Sealing plate 14 constitutesthe positive electrode terminal to act as a first terminal ofcylindrical cell 11. In the present exemplary embodiment, an outerperipheral side surface of cell case body 13 is covered with aninsulating resin film and a bottom surface of cell case body 13constitutes the negative electrode terminal. The outer peripheral sidesurface of cell case body may not be covered with an insulating resinfilm, and the cell case body may constitute a negative electrode of thecylindrical cell.

Cell holder 20 is formed from a curable resin, for example. Cell holder20 has first holder 21 to hold an upper end part of each cylindricalcell 11 and second holder 22 to hold a lower end part of eachcylindrical cell 11, with these holders coupled together. Containers 18are each formed of recess 21 a of first holder 21 and recess 22 a ofsecond holder 22. The upper end part of cylindrical cell 11 is insertedinto recess 21 a, and the lower end part of cylindrical cell 11 isinserted into recess 22 a. First and second holders 21, 22 haverespective cylindrical holes 21 b, 22 b with circular openings atlocations overlapping cylindrical cells 11 when viewed along the heightdirection. Cell module 10 may have one or more battery blocks that eachincludes one cell holder 20. Resin-made cell holder 20 may be replacedby a cell holder that is made of metal. In this case, to insulate eachcylindrical cell, insulation boards are preferably disposed between theplurality of the cylindrical cells and respective current collectorplates described next.

Positive-electrode current collector plate 30 is joined to and disposedon first holder 21 to act as a first current collector plate.Positive-electrode current collector plate 30 includes lead plate 31made of a metallic material and base plate 32 made of a metallicmaterial. Base plate 32 is joined to a top surface of lead plate 31 bywelding or other technique. Positive-electrode current collector plate30 has cylindrical holes (through holes) 30 a being put over cylindricalholes 21 b and smoothly connecting with cylindrical holes 21 b whenviewed along the height direction. Cylindrical hole 30 a has a circularopening that is substantially identical to the circular opening ofcylindrical hole 21 b. Lead plate 31 includes main plate 34 having aplurality of through holes 34 a and leads 35. Lead 35 extends from aninner surface of through hole 34 a of main plate 34 toward a center ofthrough hole 34 a and curves toward cylindrical cell 11. An end of thelead is joined to the positive electrode terminal of cylindrical cell11. Base plate 32 and main plate 34 of lead 35 constitute main body 73of positive-electrode current collector plate 30. Positive-electrodecurrent collector plate 30 includes main body 73 having cylindricalholes 30 a each put over entire safety valve 16 when viewed along theheight direction and leads 35 extending into respective cylindricalholes 30 a from main body 73 and being electrically connected to thepositive electrode terminals of cylindrical cells 11.

Meanwhile, negative-electrode current collector plate 40 is joined toand disposed beneath cell holder 20. Negative-electrode currentcollector plate 40 includes lead plate 41 made of a metallic materialand base plate 42 made of a metallic material. Base plate 42 is joinedto an undersurface of lead plate 41 by welding or other technique.Negative-electrode current collector plate 40 has cylindrical holes 40 abeing put over cylindrical holes 22 b and smoothly connecting withcylindrical holes 22 b when viewed along the height direction. Leadplate 41 includes main plate 45 having a plurality of through holes 45 aand leads 46. Lead 46 extends from an inner surface of through hole 45 aof main plate 45 toward a center of through hole 45 a and curves towardcylindrical cell 11. An end of the lead is joined to the negativeelectrode terminal of cylindrical cell 11. Consequently, the pluralityof cylindrical cells 11 is connected in parallel by positive- andnegative-electrode current collector plates 30, 40. Cell module 10 is,for example, connected in series with other cell module 10 adjacentlydisposed via a bus bar through positive- and negative-electrode currentcollector plates 30 and 40.

Positive-electrode current collector plate 30 has an area to which cellholder 20 is not joined, and insulating film 60 that is formed from aninsulating material having an insulating property, such as a resinmaterial, is disposed on the area. Insulating film 60 includes surfacecovering portion 61 to cover a surface of positive-electrode currentcollector plate 30 remote from cylindrical cells 11 in the heightdirection and cylindrical hole covering portion 62 to cover an internalcircumference of each cylindrical hole 30 a.

Exhaust duct 70 is disposed over the surface of positive-electrodecurrent collector plate 30 remote from cylindrical cells 11 in theheight direction. The plurality of cylindrical cells 11 is accommodatedin module case 80, and exhaust duct 70 is defined by an upper wall partof an inner wall surface of the module case above insulating film 60 andtop surface 66 of insulating film 60 remote from cylindrical cells 11 inthe height direction. When safety valve 16 opens, an interior ofcylindrical cell 11 communicates with exhaust duct 70 via opened safetyvalve 16, cylindrical hole 21 b of first holder 21, and cylindrical hole30 a of positive-electrode current collector plate 30. The upper wallpart for exhaust duct 70 has outlet opening 67 to communicate with anoutside. In this case, an emission including a high-temperature gas fromthe interior of cylindrical cell 11 moves through exhaust duct 70 in adirection indicated with arrow A and flows to the outside from outletopening 67.

FIG. 2 is a top plan view of a part of the cell module overlapping onecylindrical cell 11, omitting illustration of the case. FIG. 3 is a planview of the part of the cell module in FIG. 2, omitting illustration ofinsulating film 60.

As shown in FIGS. 2 and 3, safety valve 16 is disposed on an upper endface (one end face in the axis direction) of cylindrical cell 11 andincludes annular breaking portion 15 and a portion surrounded bybreaking portion 15. Annular breaking portion 15 is, for example, agroove made in a metallic plate that forms sealing plate 14. Thebreaking portion breaks first ahead of the other part of cell case 12 inresponse to a rise in internal pressure following the occurrence of anabnormality in cylindrical cell 11. Groove 17 in breaking portion 15 isgenerally called a marking that is formed by stamping cell case 12 fromoutside. A section where breaking portion 15 is formed in sealing plate14 is a thin-walled part that is thinner in thickness than the otherpart.

Safety valve 16 has the shape of a perfect circle in plan view. However,the safety valve may have the shape of an ellipse, a polygon, or anyother shape in plan view. In the present exemplary embodiment, breakingportion 15 is an annular part having a substantially constant diameterwith its center placed at a middle of the upper end face of cylindricalcell 11, such that safety valve 16 is disposed in a central region ofthe upper end face of cylindrical cell 11. If the internal pressure ofcylindrical cell 11 exceeds a predetermined level and breaking portion15 breaks, safety valve 16 opens outward from cylindrical cell 11 suchthat an opening is formed in sealing plate 14. This allows an emissionincluding a high-temperature gas to be discharged from the opening.

Insulating film 60 has straight edge 60 a substantially perpendicular toplane P that vertically divides the plan view of FIG. 2 into two equalparts. The straight edge 60 a is positioned at a distance from a tip ofthe lead. In the plan view shown in FIG. 2, insulating film 60 isannular, and an inner peripheral edge of the insulating film is made upof straight edge 60 a and circular edge 60 b that is a part of a circlejoined to both ends of straight edge 60 a. Insulating film 60 includesflange 39 overlapping a part of safety valve 16 when viewed along theheight direction. In insulating film 60, flange 39 includes projection47 that overlaps a protruding region in the height direction. Theprotruding region extends inward from the circle containing circularedge 60 b.

In safety valve 16, lead opposite region 16 a on an opposite side ofstraight edge 60 a from the lead overlaps flange 39 in the heightdirection. Part 15 a of breaking portion 15 overlapping flange 39 whenviewed along the height direction is on an opposite side of a center ofcylindrical hole 30 a (see FIG. 1) of positive-electrode currentcollector plate 30 from a lead connecting part (a part of lead 35connected to main plate 34) in a direction (indicated with arrow B)along which lead 35 extends. The part of the breaking portion ispositioned at a distance from lead 35. When viewed along the heightdirection, flange 39 overlapping part 15 a of breaking portion 15 doesnot overlap lead 35.

As shown in FIG. 3, the circular opening of cylindrical hole 30 a ofpositive-electrode current collector plate 30 is disposed concentricallywith circular groove 17 forming breaking portion 15 of safety valve 16and is larger in diameter than circular groove 17. Thus, when viewedalong the height direction, entire safety valve 16 is put overcylindrical hole 30 a of positive-electrode current collector plate 30.

With reference to FIGS. 4 and 5, operation performed by cell module 10according to the first exemplary embodiment and effects produced therebyin response to abnormal heat generation in one cylindrical cell 11 willnow be described. FIG. 4 is a schematic cross-sectional viewillustrating a problem with a structure of cell module 210 in areference example, viewed along a central axis of cylindrical cell 211with safety valve 216 opened due to abnormal heat generation. FIG. 5 isa schematic cross-sectional view of a structure corresponding to thestructure of FIG. 4 in cell module 10 according to the first exemplaryembodiment.

FIG. 4 shows an instance in which no insulating film is put on an outersurface of positive-electrode current collector plate 230. If safetyvalve 216 is opened following abnormal heat generation in cylindricalcell 211 due to, for example, a minute short circuit between a positiveelectrode and a negative electrode inside a cell case or other reason,many conductive materials contained in an emission discharged from aninterior of the cylindrical cell into exhaust duct 270 may extend fromthe interior of the cell through a part of the outer surface ofpositive-electrode current collector plate 230 facing exhaust duct 270such that path 290 of the conductive materials is formed to join thecell interior and the outer surface part together. Then, an electriccircuit originally designed in the module may be changed into a verydifferent one if electric current flows into path 290 of the conductivematerials. In addition, a large current may be hindered from flowinginto a fuse for abnormally high-temperature cylindrical cell 211, sothat the fuse is not be blown and the module cannot separate abnormallyhigh-temperature cylindrical cell 211 from the circuit of theparallel-connected cells. As a result, abnormally high-temperaturecylindrical cell 211 may further generate heat because of an electriccurrent flowing inside.

On the other hand, in cell module 10 according to the first exemplaryembodiment, an area of positive-electrode current collector plate 30facing exhaust duct 70 is covered with insulating film 60. Thus, even ifsafety valve 16 is opened following abnormal heat generation incylindrical cell 11 and an emission containing conductive materialsflows into exhaust duct 70 along a direction indicated with arrow C suchthat a path of the conductive materials is formed to join an innersurface of exhaust duct 70 and the positive electrode of cylindricalcell 11 together, insulating film 60 prevents the path of the conductivematerials from reaching positive-electrode current collector plate 30.Accordingly, even if the emission is discharged into exhaust duct 70,the positive electrode of cylindrical cell 11 is not electricallyconnected with positive-electrode current collector plate 30 by theconductive materials. Consequently, the emission from abnormallyhigh-temperature cylindrical cell 11 is hindered from forming a highresistance path and the electric circuit originally designed in themodule is not changed into a very different one.

Insulating film 60 also covers a portion of an inner circumferentialsurface of cylindrical hole 30 a of positive-electrode current collectorplate 30 other than the lead connecting part. Thus, the conductivematerials contained in the emission do not form a path between theinterior of cylindrical cell 11 and the inner circumferential surface ofcylindrical hole 30 a of positive-electrode current collector plate 30.This configuration reliably prevents the electric circuit originallydesigned in the module from being changed into a very different one.

Moreover, when viewed along the height direction, flange 39 does notoverlap lead 35, while overlapping part 15 a of breaking portion 15 (seeFIG. 2). As a result, part 15 a of breaking portion 15 overlappingflange 39 is supported by and pressed by flange 39 and is hencedifficult to be opened, so that, as shown in FIG. 5, a side of safetyvalve 16 adjacent to the lead connecting part in the lead extendingdirection is solely opened. Thus, the cell module opens the side ofsafety valve 16 adjacent to the lead connecting part and thereby cutslead 35 and separates cylindrical cell 11 that has abnormally generatedheat from the electric circuit. This configuration reliably ensuressafety of cell module 10.

In the first exemplary embodiment described above, it is preferable thatleads 46 on the negative electrode side each include a fuse to enablethe separation of a cylindrical cell that has abnormally generated heatfrom the electric circuit even if the lead on the positive electrodeside is not cut off by the opened safety valve. However, each lead 46 onthe negative electrode side may not include any fuse. Leads 35 on thepositive electrode side may each include a fuse or may not include anyfuse.

In the description given above, the insulating film covers a portion ofthe inner circumferential surface of cylindrical hole 30 a formed inpositive-electrode current collector plate 30 other than the leadconnecting part. However, the insulating film may not cover the portionof the inner circumferential surface of the through hole formed in thepositive-electrode current collector plate other than the leadconnecting part.

In the description given above, insulating film 60 does not cover backside 37 of positive-electrode current collector plate 30 adjacent tocylindrical cells 11 (an undersurface of the current collector plateremote from a side facing exhaust duct 70 in the height direction) (seeFIG. 1). However, the insulating film may cover the back side of thepositive-electrode current collector plate adjacent to the cylindricalcells (the undersurface of the current collector plate remote from aside facing the exhaust duct in the height direction). In particular, ifa cell module includes a metallic cell holder instead of resin-made cellholder 20, the cell module preferably includes an insulating boardbetween cylindrical cells 11 and a positive-electrode current collectorplate to insulate the cylindrical cells. However, it is preferable thatthe insulating film also covers the back side of the positive-electrodecurrent collector plate. This configuration prevents the formation of apath connecting the back side of the positive-electrode currentcollector plate to the interior of any of the cylindrical cells andenables an insulating layer covering the back side to insulate thecylindrical cells. This in turn allows omission of the insulating board.

In the description given above, positive-electrode current collectorplate 30 includes cylindrical holes 30 a that are each put over entiresafety valve 16 when viewed along the height direction. However, apositive-electrode current collector plate may include through holesthat each overlap at least a part of a safety valve when viewed alongthe height direction. In the description given above, insulating film 60overlaps part 15 a of annular breaking portion 15 of safety valve 16when viewed along the height direction. However, an insulating film maynot overlap any part of an annular breaking portion of a safety valvewhen viewed along the height direction.

In the description given above, the positive electrode terminal acts asthe first terminal of the cylindrical cell, and positive-electrodecurrent collector plate 30 acts as the first current collector plate.However, the negative electrode terminal may act as the first terminalof the cylindrical cell and the negative-electrode current collectorplate may act as the first current collector plate such that the safetyvalve is disposed on a bottom surface of the cylindrical cell adjacentto the negative electrode (an undersurface of the cell in the heightdirection) and the exhaust duct is disposed over a surface of thenegative-electrode current collector plate remote from the cylindricalcells. Then, an area of the negative-electrode current collector platefacing the exhaust duct may be covered with an insulating film that isformed from an insulating material such as a resin material. In additionto the area of the negative-electrode current collector plate facing theexhaust duct, the insulating film may cover a portion of an innercircumferential surface of each through hole formed in thenegative-electrode current collector plate other than the leadconnecting part. The insulating film may also cover a back side of thenegative-electrode current collector plate adjacent to the cylindricalcells.

The safety valves may be disposed on the bottom surface of thecylindrical cell adjacent to the negative electrode as well as a topsurface of the cylindrical cell adjacent to the positive electrode,respectively, such that the exhaust ducts are disposed over the surfaceof the negative-electrode current collector plate remote from thecylindrical cells as well as over the surface of the positive-electrodecurrent collector plate remote from the cylindrical cells, respectively.Then, the area of the negative-electrode current collector plate facingthe exhaust duct as well as the area of the positive-electrode currentcollector plate facing the exhaust duct may be each covered with aninsulating film that is formed from an insulating material such as aresin material. In this case as well, in addition to the area of thenegative-electrode current collector plate facing the exhaust duct, theinsulating film may cover a portion of the inner circumferential surfaceof each through hole formed in the negative-electrode current collectorplate other than the lead connecting part. The insulating film may alsocover the back side of the negative-electrode current collector plateadjacent to the cylindrical cells.

In the description given above, all the plurality of cylindrical cells11 contained in cell module 10 is connected in parallel. However, theplurality of the cylindrical cells contained in the cell module mayinclude two or more cylindrical cells that are connected in series. Thebattery cells described above are cylindrical cells 11. However, thebattery cells may be rectangular batteries.

Second Exemplary Embodiment

FIG. 6 is a schematic cross-sectional view of cell module 110 accordingto a second exemplary embodiment of the present disclosure, viewed inthe same way as FIG. 1. FIG. 7 is a schematic cross-sectional view of astructure corresponding to the structure of FIG. 5 in cell module 110according to the second exemplary embodiment. In the second exemplaryembodiment, descriptions of effects and modified examples identical tothose in the first exemplary embodiment are omitted, and structuralelements identical to those in the first exemplary embodiment areassigned with the same reference numerals and redundant descriptionsthereof are omitted.

As shown in FIG. 6, in the second exemplary embodiment, like the firstexemplary embodiment, insulating film 160 that covers a top surface ofpositive-electrode current collector plate 30 adjacent to exhaust duct170 and an inner circumferential surface of each cylindrical hole 30 aof positive-electrode current collector plate 30 includes flange 139overlapping part 115 a of breaking portion 15 when viewed along theheight direction. However, unlike the first exemplary embodiment, flange139 overlaps not only part 115 a of breaking portion 15 but also part 35a of lead 35 when viewed along the height direction. When viewed alongthe height direction, part 115 a of breaking portion 15 overlappinginsulating film 160 is positioned adjacent to lead connecting part 179and away from a center of cylindrical hole 30 a of positive-electrodecurrent collector plate 30 in a direction in which lead 35 extends.

In the second exemplary embodiment, unlike the first exemplaryembodiment, leads 146 on the negative electrode side each include fuse190. Bottom 94 of cylindrical cell 11 that constitutes a second terminalof the cylindrical cell is electrically connected to lead 146 on thenegative electrode side. In the second exemplary embodiment, unlike thefirst exemplary embodiment, outlet opening 167 of exhaust duct 170 isnot disposed on a right side of the figure but is disposed on a leftside of the figure. Other structural elements in the second exemplaryembodiment are identical to those in the first exemplary embodiment.

As shown in FIG. 7, in the second exemplary embodiment, flange 139 ofinsulating film 160 overlaps part 115 a of breaking portion 15 as wellas part 35 a of lead 35 when viewed along the height direction. Thus,part 115 a of breaking portion 15 overlapping flange 139 is supported byand pressed by flange 139 and is hence difficult to be opened, so that,as shown in FIG. 7, a side of safety valve 16 remote from the leadconnecting part in the lead extending direction is solely opened. As aresult, even if safety valve 16 opens and an emission flows along adirection indicated with arrow D, the cell module can maintain andprotect electrical connection of lead 35 to a positive electrodeterminal of cylindrical cell 11. Since insulating film 160 preventsconductive materials contained in the emission from forming a path tothe current collector plate, this configuration reliably allows a largecurrent to flow into fuse 190 at the negative electrode side ofcylindrical cell 11 that has abnormally generated heat. This enables thecell module to blow fuse 190 and hence reliably separate cylindricalcell 11 that has abnormally generated heat from an electric circuit.

REFERENCE MARKS IN THE DRAWINGS

11: cylindrical cell

12: cell case

15: breaking portion

15 a, 115 a: part of breaking portion

16: safety valve

30, 130: positive-electrode current collector plate

30 a: cylindrical hole

35: lead

35 a: part of lead

39, 139: flange

60, 160: insulating film

70, 170: exhaust duct

73: main body

190: fuse.

The invention claimed is:
 1. A cell module comprising: a plurality ofbattery cells each including: a battery element, and a cell casecontaining the battery element and having a safety valve at a first endin a height direction, the safety valve being configured to open when aninternal pressure inside the cell case reaches or exceeds apredetermined level; a first current collector plate configured toelectrically connect first terminals of the plurality of the batterycells, the first current collector plate including: a main body having athrough hole that at least partly overlaps the safety valve when viewedalong the height direction, and a lead extending into the through holefrom the main body and being electrically connected to the firstterminal of each of the battery cells; an exhaust duct disposed over asurface of the first current collector plate remote from the batterycells, the exhaust duct being configured to guide an emission beingdischarged from at least one of the plurality of the battery cells andpassing through the through hole to an outside of the cell module whenthe safety valve of the at least one battery cell is opened; and aninsulating film being made of an insulating material and covering asurface of the first current collector plate facing the exhaust duct. 2.The cell module according to claim 1, wherein the insulating film coversan inner surface of the through hole.
 3. The cell module according toclaim 1, wherein the insulating film covers a surface of the firstcurrent collector plate adjacent to the battery cells.
 4. The cellmodule according to claim 1, wherein the safety valve includes abreaking portion that is annular and that breaks when the internalpressure inside the cell case reaches or exceeds the predetermined leveland a portion surrounded by the breaking portion, wherein the lead isjoined to the safety valve, and wherein the insulating film includes aflange overlapping a part of the breaking portion when viewed along theheight direction, and the flange does not overlap the lead when viewedalong the height direction.
 5. The cell module according to claim 1,wherein the safety valve includes a breaking portion that is annular andthat breaks when the internal pressure inside the cell case reaches orexceeds the predetermined level and a portion surrounded by the breakingportion, wherein the lead is joined to the safety valve, and wherein theinsulating film includes a flange overlapping a part of the breakingportion as well as a part of the lead when viewed along the heightdirection.
 6. The cell module according to claim 2, wherein theinsulating film covers a surface of the first current collector plateadjacent to the battery cells.
 7. The cell module according to claim 2,wherein the safety valve includes a breaking portion that is annular andthat breaks when the internal pressure inside the cell case reaches orexceeds the predetermined level and a portion surrounded by the breakingportion, wherein the lead is joined to the safety valve, and wherein theinsulating film includes a flange overlapping a part of the breakingportion when viewed along the height direction, and the flange does notoverlap the lead when viewed along the height direction.
 8. The cellmodule according to claim 2, wherein the safety valve includes abreaking portion that is annular and that breaks when the internalpressure inside the cell case reaches or exceeds the predetermined leveland a portion surrounded by the breaking portion, wherein the lead isjoined to the safety valve, and wherein the insulating film includes aflange overlapping a part of the breaking portion as well as a part ofthe lead when viewed along the height direction.
 9. The cell moduleaccording to claim 3, wherein the safety valve includes a breakingportion that is annular and that breaks when the internal pressureinside the cell case reaches or exceeds the predetermined level and aportion surrounded by the breaking portion, wherein the lead is joinedto the safety valve, and wherein the insulating film includes a flangeoverlapping a part of the breaking portion when viewed along the heightdirection, and the flange does not overlap the lead when viewed alongthe height direction.
 10. The cell module according to claim 3, whereinthe safety valve includes a breaking portion that is annular and thatbreaks when the internal pressure inside the cell case reaches orexceeds the predetermined level and a portion surrounded by the breakingportion, wherein the lead is joined to the safety valve, and wherein theinsulating film includes a flange overlapping a part of the breakingportion as well as a part of the lead when viewed along the heightdirection.
 11. The cell module according to claim 6, wherein the safetyvalve includes a breaking portion that is annular and that breaks whenthe internal pressure inside the cell case reaches or exceeds thepredetermined level and a portion surrounded by the breaking portion,wherein the lead is joined to the safety valve, and wherein theinsulating film includes a flange overlapping a part of the breakingportion when viewed along the height direction, and the flange does notoverlap the lead when viewed along the height direction.
 12. The cellmodule according to claim 6, wherein the safety valve includes abreaking portion that is annular and that breaks when the internalpressure inside the cell case reaches or exceeds the predetermined leveland a portion surrounded by the breaking portion, wherein the lead isjoined to the safety valve, and wherein the insulating film includes aflange overlapping a part of the breaking portion as well as a part ofthe lead when viewed along the height direction.
 13. The cell moduleaccording to claim 1, wherein the insulating film separates the firstcurrent collector plate from the exhaust duct.
 14. The cell moduleaccording to claim 1, wherein the insulating film is disposed betweenthe first current collector plate and the exhaust duct.